[Main General Bulletin Board | BBFAQ | Post Followup ] Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos Two plugs and why Like This Post: - Subscribe to Daily Digest for this Bulletin Board Posted by Joe [Email] (#444) [Profile/Gallery] (more from Joe) on Fri, 2 Feb 2001 06:54:34 In Reply to: Not your typical spark plug question., Roger S, Thu, 1 Feb 2001 20:47:41 Alert me when someone posts in this thread: Members do not see ads below this line. - Help Keep This Site Online - Signup

Two plugs on a 4 stroke engine is not that far fetched.

On the Nissan and Ford this is done to improve drivability and meet emissions. The reduce NOx engine makers use a lot of ERG (exhaust gas recirculation) to keep the combustion temperature down. The down side is these weak mixtures are hard to light with a spark. By adding a second plug the engine doubles its chance of igniting the mixture.

All piston aircraft have dual ignition system. The biggest reason is for reliability. In the 1920's and 1930's ignitions were not too reliabile. If you make a second system you have improved the reliabality. Two plugs also improve performance by reducing burn time on inefficient domed high compression combustion chambers. As they started to add lead to the Avgas (to deal with the high compression) the plugs tended to foul. Post was Avgas has lots of lead. After 100 hours of operation the plugs have a white crust on them. With two plugs you can foul one and still get home. The two ignition systems can be turned on and off independantly so you can test each system before flying.

In the 70's and 80's it was popular to put dual plugs in BMW motorcycles. I did this on mine. It reduced the octane requirements, improved starting and added a bit of power. I believe Kawasaki drag bikes were modified for two plugs too.

Drive Safe,

Joe

• Not your typical spark plug question., Roger S, Thu, 1 Feb 2001 20:47:41
  • Mercedes and Alfa both also produce twin spark engines, Coolknight, Wed, 7 Feb 2001 05:20:13
  • Two plugs and why, Joe , Fri, 2 Feb 2001 06:54:34 <-- Viewing This Message
    • There were others (I think), hr, Fri, 2 Feb 2001 10:29:58
      • Re: There were others (I think): correctly!, andy m, Mon, 5 Feb 2001 10:06:09
      • Re: Kawasaki Vulcan 1500 cc has 2 plugs per cylinder, Mitch, Fri, 2 Feb 2001 21:58:18
    • Re: Two plugs and why, Caspar, Fri, 2 Feb 2001 09:01:32
  • Re: Not your typical spark plug question., LDH, Thu, 1 Feb 2001 22:14:55
    • Explains its gutless performance., Roger S, Thu, 1 Feb 2001 23:47:54
  • Re: Not your typical spark plug question., IrieTom , Thu, 1 Feb 2001 21:07:24

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